Different types of diagnostic devices are known in nuclear medicine. Amongst these there are the scintillation devices which basically include two categories of devices: the PET diagnostic devices and the SPECT diagnostic devices
The PET type diagnostic devices comprise a couch on which the patient lies and a measuring system with an annular shape which surrounds the patient. The couch can move axially through the measuring system for making a three-dimensional measurement. The annular measuring system has a succession of scintillation measurement devices positioned along the annular extension for identifying the antiparallel scintillation events typical of the PET technology.
The geometry used allows the patient to have a comfortable supporting surface during the examination, the duration of which can, normally, vary on the basis of the scanning area and which on average can vary from 20 to 30 minutes.
The types of devices for SPECT diagnostics also comprise a couch on which the patient lies but the measuring system does not use a ring-type geometry but adopts a square shape and rotates about a horizontal axis to perform a complete circular scan around the patient.
In the SPECT technology, the number of measuring systems normally varies as a function of the speed with which the examination is to be performed, so two or three measurement modules are often used simultaneously (normally positioned on a same rotatable support and spaced at angular intervals about the axis of rotation) for allowing a reduction in the acquisition times. The acquisition time, which varies as a function of the area to be analysed, results in lengthy times during which the patient must remain still. The standard geometry used therefore aims to acquire images in such a way that the patient remains still in the initial position and therefore avoids that a movement of the patient can change the acquisition geometry, introducing alterations to the final images produced. In this way, the use of a couch on which the patient can lie to remain still for long periods of time can ensure the achievement of this aim.
The technologies currently used therefore contemplate a use, in terms of occupation of spaces, which is certainly large, having to ensure the movement of a couch through the scanning ring and the relative shielding. Typically, the device is positioned at the centre of a medium-sized room and its installation requires a considerable overall size, to which it is necessary to add all the dimensions of the shielding systems.
To these techniques of a functional nature, the morphological technique is often also added relative to a computerised tomography TC.
Moreover, according to the current state of the art, the technologies used for performing the above-mentioned morpho-functional investigations are all oriented towards the making of devices which are able to obtain very high quality spatial resolutions. This, however, clashes with the fact that the annular measuring systems used are often designed for scanning the entire body, considering the average abdomen and chest dimensions of the patient. Generally, the dimensions of the internal diameter can be approximately 80 cm. With this reference dimension, even much smaller organs can be detected, but providing values with a lower spatial resolution, which cannot exploit the optimisations of the acquisition geometry for the specific investigation.
Moreover, the speed with which the diagnostic investigation is performed represents an important aspect in economic terms and for the management of the scintigraphic examinations.
These techniques have time limitations linked to the rapid decay of the activities of the radiopharmaceuticals (radioisotopes) used. Besides, the rapid developments resulting from research into radiopharmaceuticals have lead to increasingly specific radiopharmaceuticals linked to specific diseases. It is to be desired, however, that the use of these radiopharmaceuticals is not penalised by the excessive duration of the diagnostic examinations which could compromise the correct outcome of the examination due to the excessive decay of the pharmaceutical.